/Engine/Source/Developer/TextureFormat/Public/ChildTextureFormat.h
There are 3 ways a texture can get processed:  ITextureFormat::IsTiling returns true. This should only be for the old Oodle RAD Game Tools supplied texture encoder and is being deprecated in favor of the new built-in Oodle texture encoder (TextureFormatOodle). In this case, the child format passes the images to the encoder to split apart prior to passing to the platform tools.FChildTextureFormat::GetTilerreturns nullptr. This is being phased out because the linear version of the input texture gets encoded for each platform with a post process, wasting cook time. In this case the child format encodes the "base" texture and then tiles it using the platform tools.FChildTextureFormat::GetTilerreturns a valid pointer. This is the most recent design. In this case, the child format is used as a holder of metadata and doesn't actually do any work (CompressImage class of functions not called).
class FChildTextureFormat : public [ITextureFormat](API\Developer\TextureFormat\Interfaces\ITextureFormat)
TArray<FName>
BaseFormats
List of base formats that. Combined with FormatPrefix, this contains all formats this can handle.
constFString
FormatPrefix
Prefix put before all formats from parent formats.
TArray<FName>
SupportedFormatsCached
List of combined BaseFormats with FormatPrefix.